An [Au13]5+ Approach to the Study of Gold Nanoclusters - Inorganic

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An [Au13]5+ Approach to the Study of Gold Nanoclusters Fu Kit Sheong, Jing-Xuan Zhang, and Zhenyang Lin* Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, People’s Republic of China S Supporting Information *

ABSTRACT: Recently, many examples of gold nanoclusters have been synthesized due to their exceptional spectroscopic properties and potential applications in nanotechnology. In this work we put forward an approach based on the icosahedral [Au13]5+ unit and summarize three possible extensions of the unit: wrapping, bonding, and vertex sharing. We show that the electronic structure of such clusters can be treated in a more localized manner and show how the approach could be applied to understand the structure and bonding of a large variety of gold nanoclusters.

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examples can be viewed as the extension of a Au135+ cluster on the basis of one of the following three approaches: (a) wrapping, (b) “bonding”, and (c) vertex sharing. Here we attempt to give a unified picture, aided by a molecular orbital description, to help us better understand how orbitals and structures of such gold nanoclusters could be extended. Historically, when one is faced with clusters with valence orbitals primarily contributed by s orbitals (with also a limited number of electrons), the magic number approach is often used. In particular, these include alkali-metal18,19 and group 11 clusters.15 This approach can be understood either as the “orbitals” of a superatom20 (or a Woods−Saxon potential21) or alternatively as a linear combination of the s orbitals which gives different combinations that resemble the spherical harmonics. The applicability of this approach relies on a large s−p energy gap and limited valence electrons (or otherwise the Wade−Mingos rule applies instead), as well as minimal involvement of d orbitals.15 To understand why the superatom approach works in many group 1 and 11 spherical clusters, we will begin our discussion with a classic example: W@Au12. This is one of the clusters that has been theoretically predicted to exist22 and was later observed by experiment.23 This cluster was predicted to have an icosahedral shell of the gold atoms with an interstitial tungsten atom and serves as one of the rare examples of a bare gold cluster. To analyze this cluster, we first note that we can consider the valence orbital of an Au atom to contain only an s orbital. The d orbitals of group 11 elements are usually strongly influenced by the nucleus and do not contribute much to metal−metal bonding.24 The p orbitals of group 11 elements, however, are rather high lying and also do not contribute much to the

INTRODUCTION In the past few years, numerous different gold and silver nanoclusters have been presented in various works.1−14 Many of these clusters have unprecedented structural complexities, interesting optical properties that have aroused interest in physics and engineering, and even possible applications as catalysts or bioactive substances.3 Some of these clusters do not have a symmetrical shape, so the old rules of thumb for the bonding of clusters do not seem to apply. Because of their potential applications, a more detailed understanding of such clusters regarding their electronic structures could potentially affect a wide range of fields. Even with their widespread interest, theoretical studies are much more limited. Traditionally, the “magic number rule” applies to group 11 clusters, but previously this rule has usually been applied to a very limited number of clusters having high symmetry or resembling spherically shaped polyhedra.15 However, examples reported in recent years do not always resemble such polyhedra. Thus, simply assigning these clusters as “magic clusters” may not give enough details in describing their bonding nature and may hinder a more detailed understanding of structure and bonding as well as structure predictions. Although density functional theory (DFT) based studies have been made on some of the examples,4−6,16,17 the results are usually given as orbitals without further explanation on why particular clusters can be seen or why particular electron counts are observed. We thus see a need to extend the old rules and apply them to these new examples to allow a more effective analysis and understanding. In this short account, we will try to first use what we call an “[Au13]5+” icosahedral unit (having eight metal s electrons) to explain the structures as well as electron counts for a series of group 11 nanoclusters. We will then take this unit and try to explain more extended clusters that are challenging to explain with other methods. We can see that many of the recent © XXXX American Chemical Society

Received: August 6, 2016

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DOI: 10.1021/acs.inorgchem.6b01881 Inorg. Chem. XXXX, XXX, XXX−XXX

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extended to examples such as [C@(AuL)6]2+ 31 or the inner layers of [As@Ni12@As20]3− 32 by allowing the central atom to follow the octet rule instead of the 18-electron rule.33 Orbital analysis of the [Au13Cl2(PH3)10]3+ cluster indeed gives rise to superatom-like valence orbitals, as shown in Figure 2.

metal−metal bonding unless there exists a significant metal− ligand interaction.24 We may then consider the possible linear combination of all 12 valence s orbitals arranged in an icosahedral manner, by either applying the generator orbital approach25 or considering Stone’s surface tensor harmonics26 to construct the linear combinations (see Figure 1). Here, we

Figure 2. Representative jellium orbitals (isovalue 0.015) of [Au 1 3 (PH 3 ) 10 Cl 2 ] 3+ cluster (as a model cluster for the [Au13(PMe2Ph)10Cl2]3+ cluster 27). Note the spherical pattern enclosing the icosahedron for Sσ and the presence of a nodal plane in Pσ orbitals.

The reason clusters such as [Au13(PR3)10Cl2]3+ are also known as magic clusters is that, if we assign the formal charges to fragments of the cluster as Au +1, Cl −1, and PR3 0, we can see that the whole cluster has 8 extra valence electrons. Because 8 is one of the major “magic numbers”, such a cluster is sometimes called a “magic cluster”, “jellium cluster” or “8electron cluster”. To understand this, we may put this in the context of our ideal model in Figure 1. Because the S- and Ptype bonding orbitals are predominantly contributed by the LGOs, in this sense we can also assign these 8 electrons to the icosahedral shell, where the S and P LGOs become the 1S and 1P jellium orbitals, giving rise to the magic number of 8.

Figure 1. Qualitative orbital diagram illustrating the linear combinations of orbitals on an icosahedral surface and their interactions with the valence orbitals of an interstitial transitionmetal atom. Three selected orbitals computed from the optimized structure of W@Au12 are presented (isovalue 0.020). Note that the ag orbital and the t1u set could be assigned as the Sσ and Pσ of the superatom, while the hg set could be assigned to the interstitial center.

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can make an analogy to a standard M-LGO (metal−ligand group orbitals) approach in studying transition-metal complexes and consider the central W to be the conventional transition-metal center and the icosahedral shell as an icosahedral ligand group. We can see that the S and P combinations are clearly being stabilized, while the D combinations can also interact with the d orbitals of the central W to give bonding−antibonding pairs. Higher order combinations (i.e., the three F-type LGOs) do not have any net overlap with valence orbitals from the central W atom. We can thus deduce that the favorable orbitals are of S (predominantly from the LGO but stabilizes by the metal center), P (again predominantly from LGOs), and D type (“bonding” interaction between LGOs and the metal center). From the viewpoint of the tungsten center, it also attains the “18-electron rule”, which is ideal for most of the transition-metal complexes. However, it should be noted that bare gold clusters such as these are unstable and are unlikely to be crystallized. More commonly observed examples are the ones where each Au atom has an extra radial-pointing ligand, of which we take [Au13(PMe2Ph)10Cl2]3+ as an example.27 To extend our argument to such ligated gold clusters, we consider the valence orbitals of an AuL or AuX unit to be sp hybridized;24 the inward-pointing sp hybrid orbitals will then resemble the Au s orbitals in the W@Au12 cluster (note that they have the same irreducible representation), with the central Au atom formally fulfilling the 18-electron rule. Such an approach can be used to explain numerous gold or gold-like (with some of the gold centers replaced with other group 10−12 elements) icosahedral nanoclusters found in the literature27−30 and could be further

RESULTS AND DISCUSSION Even though this simple analysis suffices for us to identify the 8electron clusters, many identified 8-electron clusters are actually nonspherical, and it is not obvious how the orbital analysis illustrated in Figure 1 applies. A close examination of such ligated clusters reveals that not all group 11 atoms have the same number of ligands. As highlighted in Figure 3, if we consider only those gold/gold-like atoms that have no or exactly one ligand, we can see that they form one or more icosahedra (each with an interstitial Au atom inside), and we argue that all other atoms with more than one coordination can be considered simply as having +1 charge, i.e., Au(I). To understand this, we note that each gold center on the surface of the icosahedron described in Figure 1 or Figure 2 contributes either an s orbital or an sp hybrid orbital, whereas valence orbitals of higher coordinated metal centers have higher p orbital contribution (for a linear-coordinated AuL2 unit, both sp hybrid orbitals are occupied and the valence orbitals available for metal−metal interactions are pure p orbitals), and the poor interactions among the pure p orbitals of these AuL2/AuL3 units allow the simple approximation of such centers as Au(I), as also illustrated by the small contributions of such two- or three- coordinated centers to the superatom orbital shown in Figure 4. Unlike other analyses which consider the cluster as a whole,40 we made a clear separation between the icosahedral core and the peripheral gold metal centers (Au(I)) in a gold nanocluster on the basis of the coordination number. We also note that the commonly observed “aurophilicity”31,41 or “argentophilicity”42 for gold(I) and silver(I) metal centers B

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note that the interactions between two monomers are based on the linearly coordinated peripheral Au(I) centers, consistent with the observation that the distance between the two monomeric units falls within aurophilic distances instead of more prominent bonding. The count of one less valence electron than is present in [Au25(SR)18]− indicates that there is an unpaired electron in each icosahedral unit. One side note that might be pointed out here is that although in terms of electron count gold and silver (as well as other centers like Pd) could be treated on equal footing, there are actually known site preferences. As analyzed previously,46 metal atoms with stronger intermetallic interactions have higher tendencies to occupy sites with larger connectivities. This can be seen in cases presented in Figure 3 that the tendency to occupy the core decreases in the order Pd > Au > Ag. Apart from wrapping an Au13 icosahedron with AuL2 units, there are also alternative examples where we consider the merging of clusters. In particular, when gold icosahedral clusters are considered as superatoms, we can merge multiple superatoms to form a “supermolecule”, which is useful for describing 14-electron clusters (single bond) as well as 10electron clusters (triple bond). Such a united cluster approach has been described by Mingos.47 This approach is in contrast to another alternative approach to create supermolecules from superatoms, by joining the superatoms via chemical bridges.48 The orbital plots shown in Figure 5 illustrate that the set of

Figure 3. Icosahedra in selected gold and gold-like icosahedral clusters.1,8,23,27,34−38 Note that for the clusters in the top left, top right, middle right, and bottom middle panels, gold/silver centers with two or more coordinations are outside the corresponding icosahedron. All structures shown in this figure were drawn with MayaVi39 on the basis of the crystal structure (except for [W@Au12], where the optimized structure was used).

Figure 5. Illustration of selected occupied orbitals (isovalue 0.015) of two face-shared icosahedra in the Au38(SH)24 cluster (as a model cluster for the Au38(SCH2CH2Ph)24 cluster37). Note that only the inphase (Pσz + Pσz , HOMO-2) but not the out-of-phase (Pσz − Pσz , LUMO +2) combination of Pσz orbitals is occupied, resulting in a “single bond” between two “superatoms”.

Figure 4. Representative jellium orbitals (isovalue 0.015) calculated for the [Au25 (SH) 18] − cluster (as a model cluster for the [Au25(SCH2CH2Ph)18]− cluster35). Note that the valence orbitals on the icosahedral unit resemble the S and Pσz orbitals shown in Figure 2. Also note that gold atoms (shown as golden metallic spheres) in the peripheral region make a minimal contribution to the jellium orbitals in both cases.

“supermolecular orbitals” for the 14-electron cluster Au38(SH)24 resembles the in-phase/out-of-phase combinations of “superatom orbitals”, similar to the case in diatomic molecules. A similar analysis of the Au38(SR)24 cluster has also been thoroughly discussed and described by Cheng and coworkers in detail.49 Apart from merging superatoms via sharing of “magic electrons”, one can also consider vertex sharing of such superatoms (which does not occur for real atoms),50 with no sharing of magic electrons and all the in-phase and out-of-phase combinations of “superatomic” jellium orbitals are filled. As illustrated by a recent example, [Au60Se2(PPh3)10(SePh)15]+,1 one may easily analyze such clusters by counting as multiple icosahedra and then remove the double-counted atom(s) in the analysis (Figure 6). In this case, one can first consider it as five separated icosahedra and then consider the sharing of vertices, noting that all vertices should not have multiple ligand coordinations. A similar analysis could also be applied to other vertex-shared icosahedra.8,36,38,44,45

might be the reason extra gold(I)/silver(I) metal centers can wrap around an icosahedral base to form a larger cluster. Natural population analysis of the [Au25(SH)18]− cluster clearly shows three distinct groups of natural charges: the core, the icosahedron, and the peripheral gold centers, as shown in Table 1. We may apply a similar analysis to the novel example of a [Au25(SBu)180]n gold icosahedral cluster polymer,7 where we Table 1. Natural Population Analysis for [Au25(SH)18]− natural charge a

core Au

icosahedral Aua

peripheral Aua

−0.198

0.146 ± 0.004

0.377 ± 0.008

Each averaged over 12 centers. C

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of nanoclusters to allow more detailed analysis and general chemical insights to be obtained regarding the electronic properties (which is related to their physical properties and/or chemical reactivity).

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COMPUTATIONAL DETAILS

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ASSOCIATED CONTENT

All orbitals presented in this work were based on DFT calculations performed with the Guassian 09 program.51 The PBE0 density functional was chosen for all calculations.52 All Au, W, and Se centers were described by the LANL2DZ basis set with corresponding effective core potentials.53,54 Polarization functions (ζd = 0.364)55 were added for Se on top of the LANL2DZ basis set. All of the remaining atoms were treated with the 6-31G* basis set.56 All orbitals shown are based on optimized structures. The Ih and D5d symmetry point groups were imposed in the geometry optimizations of W@Au12 and [Au13(PH3)10Cl2]3+, respectively. For the computation of [Au60Se2(PH3)10(SeH)15]+, an SCF convergence criteria of 10−7 was used (10−8 default). Natural population analyses were performed using the NBO 6.0 program on the basis of the optimized structures.57 All orbital plots presented in this paper were plotted with MayaVi and Blender on the basis of the results of the DFT-based optimization. Figure 6. Selected occupied orbitals (isovalue 0.010) of the [Au60Se2(PH3)10(SeH)15]+ cluster (as a model cluster for the [Au60Se2(PPh3)10(SePh)15]+ cluster1). All five linear combinations for Sσ orbitals are occupied, as shown on the left. The Pσ orbitals also have their linear combinations occupied in a similar manner, as illustrated by the all-in-phase combination of radial Pσ as well as allout-of-phase combination of tangential Pσ jellium orbitals (HOMO) on the right.

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b01881. Cartesian coordinates of optimized geometries (PDF)

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CONCLUSIONS To summarize, we have provided a short account of a number of gold nanocluster examples and discussed how they could be analyzed. In particular, all of the clusters mentioned can be elucidated on the basis of a simple [Au13]5+ unit as well as its simple extensions (Table 2). We have discussed the effect of ligands and other gold atoms on such an icosahedral unit and illustrated how these clusters can be merged to form even larger clusters via wrapping, bonding, or vertex sharing. We anticipate that this would provide certain theoretical guidance to the study

AUTHOR INFORMATION

Corresponding Author

*E-mail for Z.L.: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the Research Grants Council of Hong Kong (N_HKUST603/15). F.K.S. acknowledges support

Table 2. Decompositions of Selected Examples cluster [Au13Cl2(PMe2Ph)10]3+ 27 [Au9Ag4Cl4(PMePh2)8]+ 28 [(Ph3PAu)6(dppeAu2)(AuCl)4Pd]29 [Au9Cu4Cl4(PMePh2)8]+ 30 [(Ph3P)6Au6Ag6Pt(AgI3)2]2+ 34 [Au19(PhCC)9(Hdppa)3]2+ 6 [Ag21{S2P(OiPr)2}12]+ 43 [Au25(SCH2CH2Ph)18]− 35 [PdAg24(2,4-SPhCl2)18]2− 2 [Ag25(SPhMe2)18]− 3 [CdAu24(SC2H4Ph)18]5 [Au25(SBu)180]n7 [Pt2(AuPPh3)10Ag13Cl7]36 [(Ph3P)10Au12Ag12NiCl7]+ 44 [(MePh2P)10Au12Ag13Br9]45 [Au38(SCH2CH2Ph)24]37 [Au37(PPh3)10(SC2H4Ph)10Cl2]+ 8 [(p-Tol3P)12Au18Ag20Cl14]38 [Au60Se2(PPh3)10(SePh)15]+ 1

no. of peripheral Au(I)/Ag(I) centers

decomposition

jellium electron count

one icosahedron

0

8

one wrapped icosahedron one wrapped icosahedron one wrapped icosahedron

2 6 8

8 8 8

one wrapped icosahedron

12

8

wrapped icosahedra held together by aurophilic interaction

8n

7n

two vertex-shared icosahedra

0

8 × 2 = 16

wrapped two face-shared icosahedra linearly arranged three vertex-shared icosahedra wrapped triangularly arranged three vertex-shared icosahedra pentagonally arranged five vertex-shared icosahedra

15 0 2 0

(8 × 2) − 2 = 14 8 × 3 = 24 8 × 3 = 24 8 × 5 = 40

D

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(19) Knight, W. D.; de Heer, W. A.; Clemenger, K.; Saunders, W. A. Electronic Shell Structure in Potassium Clusters. Solid State Commun. 1985, 53 (5), 445−446. (20) Luo, Z.; Castleman, A. W. Special and General Superatoms. Acc. Chem. Res. 2014, 47, 2931. (21) Woods, R. D.; Saxon, D. S. Diffuse Surface Optical Model for Nucleon-Nuclei Scattering. Phys. Rev. 1954, 95 (2), 577−578. (22) Pyykkö, P.; Runeberg, N. Icosahedral WAu12: A Predicted Closed-Shell Species, Stabilized by Aurophilic Attraction and Relativity and in Accord with the 18-Electron Rule. Angew. Chem., Int. Ed. 2002, 41 (12), 2174−2176. (23) Li, X.; Kiran, B.; Li, J.; Zhai, H.-J.; Wang, L.-S. Experimental Observation and Confirmation of Icosahedral W@Au12 and Mo@Au12 Molecules. Angew. Chem., Int. Ed. 2002, 41 (24), 4786−4789. (24) Lin, Z.; Kanters, R. P. F.; Mingos, D. M. P. Closed-Shell Electronic Requirements for Condensed Clusters of the Group 11 Elements. Inorg. Chem. 1991, 30 (1), 91−95. (25) Verkade, J. G. A Pictorial Approach to Molecular Bonding; Springer US: New York, 1986. (26) Stone, A. J. New Approach to Bonding in Transition-Metal Clusters and Related Compounds. Inorg. Chem. 1981, 20 (2), 563− 571. (27) Briant, C. E.; Theobald, B. R. C.; White, J. W.; Bell, L. K.; Mingos, D. M. P.; Welch, A. J. Synthesis and X-Ray Structural Characterization of the Centred Icosahedral Gold Cluster Compound [Aul3(PMe2Ph)10Cl2](PF6)3; the Realization of a Theoretical Prediction. J. Chem. Soc., Chem. Commun. 1981, No. 5, 201−202. (28) Copley, R. C. B.; Mingos, D. M. P. Synthesis and Structural Characterization of [Au 9 Ag 4 Cl 4 (PMePh 2 ) 8 ][C 2 B 9 H 12 ]·H 2 O· 0.5CH2Cl2: The First Example of an Icosahedral Silver−gold Cluster. J. Chem. Soc., Dalton Trans. 1992, No. 10, 1755−1756. (29) Laupp, M.; Strähle, J. [(Ph3PAu)6(dppeAu2) (AuCl)4Pd], an Icosahedral Au12 Cluster with a Central Pd Atom. Angew. Chem., Int. Ed. Engl. 1994, 33 (2), 207−209. (30) Copley, R. C. B.; Mingos, D. M. P. Synthesis and Characterization of the Centred Icosahedral Cluster Series [Au9MIB4Cl4(PMePh2)8][C2B9H12], Where MIB= Au, Ag or Cu. J. Chem. Soc., Dalton Trans. 1996, No. 4, 491−500. (31) Scherbaum, F.; Grohmann, A.; Huber, B.; Krüger, C.; Schmidbaur, H. Aurophilicity” as a Consequence of Relativistic Effects: The Hexakis(triphenylphosphaneaurio)methane Dication [(Ph3PAu)6C]2+. Angew. Chem., Int. Ed. Engl. 1988, 27 (11), 1544− 1546. (32) Moses, M. J.; Fettinger, J. C.; Eichhorn, B. W. Interpenetrating As20 Fullerene and Ni12 Icosahedra in the Onion-Skin [As@Ni12@ As20]3− Ion. Science 2003, 300 (5620), 778−780. (33) Sheong, F. K.; Chen, W.-J.; Kim, H.; Lin, Z. Peeling the Onion: A Revised Model of the Electron Count for Matryoshka Clusters. Dalton Trans. 2015, 44 (16), 7251−7257. (34) Teo, B. K.; Zhang, H. Molecular and Crystal Structure of an Iodo-Gold-Silver-Platinum Cluster, [(Ph3 P) 6 Au 6 Ag6 Pt(AgI 3 ) 2 ](THF)2, with a Trimetallic Icosahedral Core Capped with Two Planar [AgI3] Units. J. Organomet. Chem. 2000, 614−615, 66−69. (35) Heaven, M. W.; Dass, A.; White, P. S.; Holt, K. M.; Murray, R. W. Crystal Structure of the Gold Nanoparticle [N(C8H17)4][Au25(SCH2CH2Ph)18]. J. Am. Chem. Soc. 2008, 130 (12), 3754−3755. (36) Kappen, T. G. M. M.; Schlebos, P. P. J.; Bour, J. J.; Bosman, W. P.; Smits, J. M. M.; Beurskens, P. T.; Steggerda, J. J. A New 25-MetalAtom Supracluster: Synthesis, Characterization, and Crystal Structure of the Ternary Cluster Compound [Pt2(AuPPh3)10Ag13Cl7]. Inorg. Chem. 1994, 33 (4), 754−758. (37) Qian, H.; Eckenhoff, W. T.; Zhu, Y.; Pintauer, T.; Jin, R. Total Structure Determination of Thiolate-Protected Au38 Nanoparticles. J. Am. Chem. Soc. 2010, 132 (24), 8280−8281. (38) Teo, B. K.; Zhang, H.; Shi, X. Cluster of Clusters: A Modular Approach to Large Metal Clusters. Structural Characterization of a 38Atom Cluster [(p-Tol3P)12Au18Ag20Cl14] Based on Vertex-Sharing Triicosahedra. J. Am. Chem. Soc. 1990, 112 (23), 8552−8562.

from the Hong Kong Ph.D. Fellowship Scheme 2012/13 (PF11-08816).

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REFERENCES

(1) Song, Y.; Fu, F.; Zhang, J.; Chai, J.; Kang, X.; Li, P.; Li, S.; Zhou, H.; Zhu, M. The Magic Au60 Nanocluster: A New Cluster-Assembled Material with Five Au13 Building Blocks. Angew. Chem., Int. Ed. 2015, 54 (29), 8430−8434. (2) Yan, J.; Su, H.; Yang, H.; Malola, S.; Lin, S.; Häkkinen, H.; Zheng, N. Total Structure and Electronic Structure Analysis of Doped Thiolated Silver [MAg24(SR)18]2− (M = Pd, Pt) Clusters. J. Am. Chem. Soc. 2015, 137 (37), 11880−11883. (3) Joshi, C. P.; Bootharaju, M. S.; Alhilaly, M. J.; Bakr, O. M. [Ag25(SR)18]−: The “Golden” Silver Nanoparticle. J. Am. Chem. Soc. 2015, 137 (36), 11578−11581. (4) Kwak, K.; Tang, Q.; Kim, M.; Jiang, D.; Lee, D. Interconversion between Superatomic 6-Electron and 8-Electron Configurations of M@Au24(SR)18 Clusters (M = Pd, Pt). J. Am. Chem. Soc. 2015, 137 (33), 10833−10840. (5) Wang, S.; Song, Y.; Jin, S.; Liu, X.; Zhang, J.; Pei, Y.; Meng, X.; Chen, M.; Li, P.; Zhu, M. Metal Exchange Method Using Au25 Nanoclusters as Templates for Alloy Nanoclusters with Atomic Precision. J. Am. Chem. Soc. 2015, 137 (12), 4018−4021. (6) Wan, X.-K.; Tang, Q.; Yuan, S.-F.; Jiang, D.; Wang, Q.-M. Au19 Nanocluster Featuring a V-Shaped Alkynyl−Gold Motif. J. Am. Chem. Soc. 2015, 137 (2), 652−655. (7) De Nardi, M.; Antonello, S.; Jiang, D.; Pan, F.; Rissanen, K.; Ruzzi, M.; Venzo, A.; Zoleo, A.; Maran, F. Gold Nanowired: A Linear (Au25)n Polymer from Au25 Molecular Clusters. ACS Nano 2014, 8 (8), 8505−8512. (8) Jin, R.; Liu, C.; Zhao, S.; Das, A.; Xing, H.; Gayathri, C.; Xing, Y.; Rosi, N. L.; Gil, R. R.; Jin, R. Tri-Icosahedral Gold Nanocluster [Au37(PPh3)10(SC2H4Ph)10X2]+: Linear Assembly of Icosahedral Building Blocks. ACS Nano 2015, 9 (8), 8530−8536. (9) Liu, C.; Li, T.; Li, G.; Nobusada, K.; Zeng, C.; Pang, G.; Rosi, N. L.; Jin, R. Observation of Body-Centered Cubic Gold Nanocluster. Angew. Chem., Int. Ed. 2015, 54 (34), 9826−9829. (10) Wan, X.-K.; Yuan, S.-F.; Tang, Q.; Jiang, D.; Wang, Q.-M. Alkynyl-Protected Au23 Nanocluster: A 12-Electron System. Angew. Chem., Int. Ed. 2015, 54 (20), 5977−5980. (11) Wan, X.-K.; Xu, W. W.; Yuan, S.-F.; Gao, Y.; Zeng, X.-C.; Wang, Q.-M. A Near-Infrared-Emissive Alkynyl-Protected Au24 Nanocluster. Angew. Chem., Int. Ed. 2015, 54 (33), 9683−9686. (12) Chen, Y.; Zeng, C.; Liu, C.; Kirschbaum, K.; Gayathri, C.; Gil, R. R.; Rosi, N. L.; Jin, R. Crystal Structure of Barrel-Shaped Chiral Au130(p-MBT)50 Nanocluster. J. Am. Chem. Soc. 2015, 137 (32), 10076−10079. (13) Takano, S.; Yamazoe, S.; Koyasu, K.; Tsukuda, T. SlowReduction Synthesis of a Thiolate-Protected One-Dimensional Gold Cluster Showing an Intense Near-Infrared Absorption. J. Am. Chem. Soc. 2015, 137 (22), 7027−7030. (14) Jin, R.; Zeng, C.; Zhou, M.; Chen, Y. Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities. Chem. Rev. 2016, 116 (18), 10346−10413 and references therein. (15) Mingos, D. M. P.; Slee, T.; Lin, Z. Bonding Models for Ligated and Bare Clusters. Chem. Rev. 1990, 90 (2), 383−402. (16) Wickramasinghe, S.; Atnagulov, A.; Yoon, B.; Barnett, R. N.; Griffith, W. P.; Landman, U.; Bigioni, T. P. M 3 Ag 17 (SPh) 12 Nanoparticles and Their Structure Prediction. J. Am. Chem. Soc. 2015, 137 (36), 11550−11553. (17) Malola, S.; Lehtovaara, L.; Häkkinen, H. A DFT Study of Linear Gold−Thiolate Superclusters Absorbing in the Therapeutic NIR Window. J. Phys. Chem. Lett. 2014, 5 (8), 1329−1334. (18) Knight, W. D.; Clemenger, K.; de Heer, W. A.; Saunders, W. A.; Chou, M. Y.; Cohen, M. L. Electronic Shell Structure and Abundances of Sodium Clusters. Phys. Rev. Lett. 1984, 52 (24), 2141−2143. E

DOI: 10.1021/acs.inorgchem.6b01881 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry (39) Ramachandran, P.; Varoquaux, G. Mayavi: 3D Visualization of Scientific Data. Comput. Sci. Eng. 2011, 13 (2), 40−51. (40) Aikens, C. M. Geometric and Electronic Structure of Au25(SPhX)18− (X = H, F, Cl, Br, CH3, and OCH3). J. Phys. Chem. Lett. 2010, 1 (17), 2594−2599. (41) Schmidbaur, H. The Aurophilicity Phenomenon: A Decade of Experimental Findings, Theoretical Concepts and Emerging Applications. Gold Bull. 2000, 33 (1), 3−10. (42) Che, C.-M.; Tse, M.-C.; Chan, M. C. W.; Cheung, K.-K.; Phillips, D. L.; Leung, K.-H. Spectroscopic Evidence for Argentophilicity in Structurally Characterized Luminescent Binuclear Silver(I) Complexes. J. Am. Chem. Soc. 2000, 122 (11), 2464−2468. (43) Dhayal, R. S.; Liao, J.-H.; Liu, Y.-C.; Chiang, M.-H.; Kahlal, S.; Saillard, J.-Y.; Liu, C. W. [Ag21{S2P(OiPr)2}12]+: An Eight-Electron Superatom. Angew. Chem., Int. Ed. 2015, 54 (12), 3702−3706. (44) Teo, B. K.; Zhang, H.; Shi, X. Site Preference in Vertex-Sharing Polyicosahedral Supraclusters Containing Groups 10 and 11 Metals and Their Bonding Implications: Syntheses and Structures of the First Au-Ag-M (M = Pt, Ni) Biicosahedral Clusters [(Ph3P)10Au12Ag12PtCl7]Cl and [(Ph3P)10Au12Ag12NiCl7](SbF6). Inorg. Chem. 1994, 33 (18), 4086−4097. (45) Teo, B. K.; Dang, H.; Campana, C. F.; Zhang, H. Synthesis, Structure, and Characterization of (MePh2P)10Au12Ag13Br9: The First Example of a Neutral Bi-Icosahedral Au-Ag Cluster with a Novel Seven-Membered Satellite Ring of Bridging Ligands. Polyhedron 1998, 17 (4), 617−621. (46) Mingos, D. M. P.; Lin, Z. Site Preference Effects in Heterometallic Clusters. Comments Inorg. Chem. 1989, 9 (2), 95−122. (47) Mingos, D. M. P. Structural and Bonding Patterns in Gold Clusters. Dalton Trans. 2015, 44 (15), 6680−6695. (48) Champsaur, A. M.; Velian, A.; Paley, D. W.; Choi, B.; Roy, X.; Steigerwald, M. L.; Nuckolls, C. Building Diatomic and Triatomic Superatom Molecules. Nano Lett. 2016, 16 (8), 5273−5277. (49) Cheng, L.; Ren, C.; Zhang, X.; Yang, J. New Insight into the Electronic Shell of Au38(SR)24: A Superatomic Molecule. Nanoscale 2013, 5 (4), 1475−1478. (50) Teo, B. K.; Zhang, H. Cluster of Clusters: Structural Rules for Vertex-Sharing Icosahedral Supraclusters. J. Cluster Sci. 1990, 1 (2), 223−228. (51) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö .; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision D.01; Gaussian Inc., Wallingford, CT, 2009. (52) Adamo, C.; Barone, V. Toward Reliable Density Functional Methods without Adjustable Parameters: The PBE0Model. J. Chem. Phys. 1999, 110 (13), 6158−6170. (53) Wadt, W. R.; Hay, P. J. Ab Initio Effective Core Potentials for Molecular Calculations. Potentials for Main Group Elements Na to Bi. J. Chem. Phys. 1985, 82 (1), 284. (54) Hay, P. J.; Wadt, W. R. Ab Initio Effective Core Potentials for Molecular Calculations. Potentials for K to Au Including the Outermost Core Orbitals. J. Chem. Phys. 1985, 82 (1), 299. (55) Höllwarth, A.; Böhme, M.; Dapprich, S.; Ehlers, A. W.; Gobbi, A.; Jonas, V.; Köhler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G. A Set of D-Polarization Functions for Pseudo-Potential Basis Sets of the Main Group Elements Al-Bi and F-Type Polarization Functions for Zn, Cd, Hg. Chem. Phys. Lett. 1993, 208 (3−4), 237−240.

(56) Hariharan, P. C.; Pople, J. A. The Influence of Polarization Functions on Molecular Orbital Hydrogenation Energies. Theor. Chim. Acta 1973, 28 (3), 213−222. (57) Glendening, E. D.; Landis, C. R.; Weinhold, F. NBO 6.0: Natural Bond Orbital Analysis Program. J. Comput. Chem. 2013, 34 (16), 1429−1437.

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DOI: 10.1021/acs.inorgchem.6b01881 Inorg. Chem. XXXX, XXX, XXX−XXX